Commercial baking ovens for large volume baking are sometimes referred to as tunnel ovens. Trays of food products are circulated through the oven chamber (the tunnel) by conveyor system using endless chains connected to opposing lateral sides of the trays. The food products are typically baked using convection, conduction, radiation with turbulence, or some combination thereof. The combination of the high heat, in addition to the moisture which is evaporated from the food product as a result of the baking process, can create challenges relative to maintaining proper lubrication of the chains conveying the trays of products. Proper lubrication is critically important to oven maintenance as the conveyor chains could prematurely wear, and/or seize. Malfunction of the chains can create a serious oven failure with the attendant loss of productivity, cost of repair, and inconvenience.
Such ovens are traditionally lubricated with a graphite type lubricant. This lubricant is mixed with a carrier fluid and then applied to the chain when the oven has cooled to ambient temperature. The lubricant is applied manually with a spray applicator, and as the oven temperature rises, the carrier evaporates and the residual graphite lubricates the chain. There are several problems with this system. One problem is that the cooling of the oven requires oven downtime, which reduces the productivity and throughput of the oven equipment and corresponding return on investment. Another problem is that the graphite can end up collecting at various points in the oven which leads to an unclean worksite, and can end up in the products. Yet another problem with this method of lubrication is that it requires periodic scheduling of the oven downtime and the associated manual labor. The associated expense and loss of productivity are disincentives to proper routine maintenance of the conveyor. Failure to lubricate on a regular basis can lead to shortened equipment lifetime and/or equipment failure.
Lubricants used in food-processing machinery must be approved by the federal Food and Drug Administration because of the possibility that small amounts of such lubricants will contact the food. The U.S. Department of Agriculture (U.S.D.A.) Food Safety Inspection Service formerly certified lubricants suitable for use in food processing and handling plants. In 1999, NSF International® launched the NSF Nonfood Compounds Registration and Listing Program to provide an independent certification program to fill the void created by discontinuance of the U.S.D.A. list. All compounds that were on the U.S.D.A. list were carried over to the NSF program. Lubricants can be registered as NSF H1 or H2.
An NSF H1 lubricant is acceptable as a lubricant with incidental food contact (H1) for use in and around food processing areas. Such compounds may be used on food processing equipment as a lubricant for machine parts and equipment in locations in which there is a potential exposure of the lubricated part to food. The compounds must be formulated in compliance with 21 C.F.R. section 178.3570 and other sections referenced therein. The amount used should be the minimum required to accomplish the desired technical effect on the equipment.
An NSF H2 lubricant is acceptable as a lubricant where there is no possibility of food contact (H2) in and around food processing areas. Such compounds may be used as lubricants on equipment and machine parts in locations in which there is no possibility of the lubricant or lubricated part contacting edible products.
High production conveyor food ovens are severely extreme environments in terms of wear, corrosion and high temperature conditions. The conveyor drive chains in these baking ovens may require an NSF H1 lubricant because of the potential of exposure to edible products; however, many NSF H1 lubricants (e.g., mineral oil based lubricants) can not be used at the high operating temperatures typical of ovens. Synthetic lubricants can offer advantages over mineral oil based lubricants (e.g., chain cleanliness, low volatility and excellent anti-wear protection); however, it may be difficult to obtain NSF H1 registration for a synthetic lubricant capable of operating at high temperatures.
What is needed in the art is a method and apparatus for dispensing lubricant accurately to wear points located on a conveyor chain, or, which does not require downtime of the oven or other equipment and which can provide the lubrication automatically.